Apparatus and method for a molded waveguide for use with touch screen displays

ABSTRACT

An apparatus and method for an inexpensive, simple to make, self-aligning molded waveguide made of an optically transparent material and that can be used to generate a grid or lamina of light for use with touch screen displays. The molded waveguide substrate includes a plurality of lenses and a plurality of waveguide grooves corresponding to the plurality of integral lenses respectively. After the substrate is molded, the grooves are filled with an optically transparent material to optically couple and align the plurality of lenses and the plurality of grooves respectively. In one application, the molded waveguide substrate is positioned adjacent a touch screen device. A light transmitter and an imaging device are optically coupled to the molded waveguide substrate, and a processing device is coupled to the imaging device. The processing device is configured to determine a data entry to the touch screen by deciphering the coordinates of an interrupt in the light created in the free space adjacent the touch screen device when a data entry is being made to the touch screen device.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates generally to light generation andreception for touch screen displays, and more particularly, to aninexpensive, simple to make, self-aligning molded waveguide array madeof an optically transparent material that can be used to generate a gridor lamina of light and receive the light for detection with touch screendisplays.

2. Description of the Related Art

User input devices for data processing systems can take many forms. Twotypes of relevance are touch screens and pen-based screens. With eithera touch screen or a pen-based screen, a user may input data by touchingthe display screen with either a finger or an input device such as astylus or pen.

One conventional approach to providing a touch or pen-based input systemis to overlay a resistive or capacitive film over the display screen.This approach has a number of problems. Foremost, the film causes thedisplay to appear dim and obscures viewing of the underlying display. Tocompensate, the intensity of the display screen is often increased.However, in the case of most portable devices, such as cell phones,personal digital assistants, and laptop computers, the added intensityrequires additional power, reducing the life of the battery of thedevice. The films are also easily damaged. In addition, the cost of thefilm scales dramatically with the size of the screen. With largescreens, the cost is therefore typically prohibitive.

Another approach to providing touch or pen-based input systems is to usean array of source Light Emitting Diodes (LEDs) along two adjacent X-Ysides of an input display and a reciprocal array of correspondingphotodiodes along the opposite two adjacent X-Y sides of the inputdisplay. Each LED generates a light beam directed to the reciprocalphotodiode. When the user touches the display, with either a finger orpen, the interruptions in the light beams are detected by thecorresponding X and Y photodiodes on the opposite side of the display.The data input is thus determined by calculating the coordinates of theinterruptions as detected by the X and Y photodiodes. This type of datainput display, however, also has a number of problems. A large number ofLEDs and photodiodes are required for a typical data input display. Theposition of the LEDs and the reciprocal photodiodes also need to bealigned. The relatively large number of LEDs and photodiodes, and theneed for precise alignment, make such displays complex, expensive, anddifficult to manufacture.

Yet another approach involves the use of polymer waveguides to bothgenerate and receive beams of light from a single light source to asingle array detector. These systems tend to be complicated andexpensive and require two kinds of alignment, between the transmit andreceive waveguides and between the lenses and the waveguides. Thewaveguides are usually made using a lithographic process that can beexpensive or difficult to source.

Accordingly, there is a need for an inexpensive, simple to make,self-aligning or no alignment required molded waveguide made of anoptically transparent material and that can be used to generate a gridor lamina of light for use with touch screen displays.

SUMMARY OF THE INVENTION

The present invention relates to an apparatus and method for aninexpensive, simple to make, molded waveguide array made of an opticallytransparent material and that can be used to generate a grid or laminaof light for use with touch screen displays. The molded waveguidesubstrate includes a plurality of molded lenses and a plurality ofwaveguide grooves corresponding to and aligned with the plurality ofintegral lenses respectively. After the substrate is molded, the groovesare filled with an optically transparent material to optically coupleand align the plurality of lenses and the plurality of groovesrespectively. In one application, the molded waveguide substrate ispositioned adjacent a touch screen device. A light transmitter and animaging device are optically coupled to the molded waveguide substrate,and a processing device is coupled to the imaging device. The processingdevice is configured to determine a data entry to the touch screen bydeciphering the coordinates of an interrupt in the light created in thefree space adjacent the touch screen device when a data entry is beingmade to the touch screen device.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention, together with further advantages thereof, may best beunderstood by reference to the following description taken inconjunction with the accompanying drawings in which:

FIG. 1 is a touch screen display device.

FIG. 2 is a top view of a molded waveguide for use with the touch screendisplay device according to the present invention.

FIG. 3 is a front enlarged view of a lens and waveguide on the moldedwaveguide according to the present invention.

FIG. 4 is a cross-section view of a lens and waveguide on the moldedwaveguide of the present invention.

FIG. 5 is a perspective view of the molded waveguide according toanother embodiment of the present invention.

FIG. 6 is another perspective view of the molded waveguide according toyet another embodiment of the present invention.

FIG. 7 is a flow diagram illustrating the steps of making the moldedwaveguide according to the present invention.

FIG. 8 through 8D show the structure at each step of making the moldedwaveguides as specified in FIG. 7 and according to the presentinvention.

In the figures, like reference numbers refer to like components andelements.

DETAILED DESCRIPTION OF THE INVENTION

Referring to FIG. 1, a touch screen data input device is shown. The datainput device 10 defines a continuous sheet or “lamina” 12 of light inthe free space adjacent to a touch screen 14. The lamina 12 of light iscreated by an X and Y input light sources 16 and 18 respectively. Anoptical position detection device 20, optically coupled to the lamina oflight, is provided to detect data entries to the input device bydetermining the location of interrupts in the lamina caused when data isentered to the input device. The optical position detection device 20includes an X receive array 22, a Y receive array 24 and a processor 26.During operation, a user makes a data entry to the device 10 by touchingthe screen 14 using an input device, such as a finger, pen or stylus.During the act of touching the screen, the lamina 12 of light in thefree space adjacent the screen is interrupted. The X receive array 22and Y receive array 24 of the optical position detection device 20detect the X and Y coordinates of the interrupt. Based on thecoordinates, the processor 26 determines the data entry to the device10. For more information on the data entry device 10, see co-pending,U.S. application Ser. No. 10/817,564, entitled Apparatus and Method fora Data Input Device Using a light Lamina Screen and an Optical PositionDigitizer and filed on Apr. 1, 2004, incorporated by reference hereinfor all purposes.

FIG. 2 is a top view of a molded waveguide substrate for use with thedata entry device 10 according to the present invention. The waveguidesubstrate 30 in the embodiment shown includes X and Y light input sides32 and 34 and X and Y light receiving sides 36 and 38. Each side 32-38includes a plurality of lenses 40. Each lens 40 is optically coupled toa waveguide 42. The waveguides 42 are grooves formed in the waveguidesubstrate 30. The grooves are filled with an optically transparentmaterial having an index of refraction higher than the waveguidesubstrate 30. A first sub-set 42 a of the waveguides 42 are opticallycoupled to a light transmitter 44, such as a Vertical Cavity SurfaceEmitting Laser (VCSEL). The first sub-set of waveguides 42 a areresponsible for guiding light generated by the transmitter 44 to thecorresponding lenses 40 along the X and Y light input sides 32 and 34respectively. A coupling horn 45, made of a high index of refractionmaterial, is positioned between the light transmitter 44 and the inputsof the waveguides 42 a. The coupling horn is responsible for controllingor directing the light from the transmitter 44 to the light inputs ofthe waveguides 42 b. The light exiting the lenses 40 along the X and Ylight input sides 32 and 34 creates a plane or lamina 12 of lightbetween the four sides 32-38 of the waveguide substrate 30. A secondsub-set 42 b of the waveguides 42 are optically coupled to an imagingdevice 48, such as a MOS imaging chip or a Charge Coupled Device (CCD).The second set of waveguides 42 b are responsible for guiding lightreceived by the lenses 40 along the X and Y light receiving sides 36 and38 to the imaging device 48.

The waveguide substrate 30 may be used with the data entry device 10described above. In this embodiment, the waveguide substrate 30 ispositioned adjacent the touch screen 14. The light transmitter 44 andthe imaging device 48 are optically coupled to the waveguides 42 a and42 b of substrate 30 respectively. During operation, the lamina 12 oflight is created in the free space adjacent the touch screen 14 by thelight transmitted from the X and Y light input sides 32 and 34 of thesubstrate 30. More specifically, light from the transmitter 44 is guidedthrough the waveguides 42 a to the lenses 40 along the X and Y lightinput sides 32 and 34 respectively. During the act of touching thescreen, the lamina 12 of light in the free space adjacent the screen 14is interrupted. The lenses 40 along the X and Y light receive sides 36and 38 focus light from the lamina 12 into their respective waveguides42 b to the imaging device 48. The lenses 40 in the optical path of aninterrupt will typically receive little or no lamina light (i.e., ashadow). The imaging device 48 converts the received light signals fromthe waveguides 42 b to corresponding electrical signals. The magnitudeof the electrical signals corresponding to the waveguides 42 b thatreceive little or no light due to a shadow or interrupt in the lamina 12are different than the electrical signals corresponding to waveguides 42b that receive non-blocked lamina light. Based on this difference inmagnitude, the processor 26 (not shown), coupled to the imaging device48, determines the X and Y coordinates of the data entry to the device10.

In various embodiments, the lenses 40 are three dimensional and can haveoptical properties resulting in the creation of a lamina 12 as describedabove or a grid of light. For more details using a grid of light for adata input device, see U.S. Pat. No. 5,914,709, incorporated byreference herein for all purposes. For more details on the lenses 40,see co-pending, commonly assigned U.S. application Ser. No. 10/862,007entitled “TECHNIQUES FOR MANUFACTURING A WAVEGUIDE WITH ATHREE-DIMENSIONAL LENS” filed Jun. 4, 2004, and co-pending, commonlyassigned U.S. application Ser. No. 10/862,003 entitled “WAVEGUIDE WITH ATHREE-DIMENSIONAL LENS” filed Jun. 4, 2004, also incorporated herein byreference for all purposes.

Referring to FIG. 3, an enlarged front view of a lens 40 and waveguide42 on the waveguide substrate 30 according to the present invention isshown. As illustrated in the figure, the base of the lens surface 42 ais flush with the surface 30 a of the waveguide substrate 30. The body(not shown) of the lens tapers backward to the waveguide groove 42.

Referring to FIG. 4, a perspective cross section view of a lens 40 andwaveguide 42 on the waveguide substrate 30 according to the presentinvention is shown. In this view, the molded lens 40 is molded with thewaveguide substrate 30. This curvature aids the lens 40 in focusingreceived light at the entrance 43 of the waveguide 42. As described inmore detail below, the waveguides 42 are formed by grooves formed in thesubstrate 30 which are filed with an optically transparent material. Inan alternative embodiment, the lens 40 is formed in a half-circularshape. Such a configuration would have preferable optical propertiesover that shown in FIG. 4. However, the half-circular shape would bemore difficult to mold and would result in an undercut region at thelens-substrate interface.

FIG. 5 is a perspective view of the waveguide substrate 30 according toanother embodiment of the present invention. In this embodiment, thegrooves used to form the waveguides 42 are provided on both the top(i.e., a first axis) surface 30 a and a side surface 30 b (i.e., asecond axis) of the substrate 30. This features may be used insituations where it may be beneficial to mount a device 50, such as atransmitter and/or an imaging device, to the side of the substrate 30.This arrangement is typically beneficial in situations where it isdesirable to mount the light transmitter 44 and/or imaging device 48co-planar with the substrate. In this specific embodiment, the two axisare perpendicular to one another. However, it should be noted that thewaveguides 42 may be routed to any side or surface of the substrate 30as needed. For example, the waveguides 42 could be routed from the topsurface to the bottom surface or any side surface of the waveguidesubstrate 30.

In one embodiment, the edges of the substrate 30 adjacent the lenses 40may be scalloped. This feature is illustrated in FIG. 5. The edges 52 ofthe substrate 30 may also be rounded or curved at locations where thewaveguides 42 extend over two surface of the substrate 30, asillustrated in FIG. 5. The rounded edges tend to improve the opticalperformance of the waveguides compared to squared edges.

FIG. 6 is another perspective view of the molded waveguide according toyet another embodiment of the present invention. In this embodiment, thefirst sub-set 42 a and the second sub-set 42 b of waveguides 42 areterminated at adjacent locations on the top surface 30 a of thesubstrate 30. This embodiment is convenient because it allows both alight transmitting device 44 and an imaging device 48 to be mounted on asingle substrate 60 at one location (as opposed to spaced locations asshown in FIG. 1). Again, with this embodiment, the waveguides 42 may beterminated on the top surface 30 a of the substrate 30, any side surface(i.e., 30 b as illustrated in FIG. 5), or even the bottom surface of thesubstrate 30.

FIG. 7 is a flow diagram 70 illustrating the steps of making thewaveguide 30 according to the present invention. FIG. 8A-8D shows in thewaveguide structure at each step defined in the flow chart of FIG. 7. Inthe initial step 72, the substrate 30 is molded using either injectionor compression molding. With either embodiment, the lenses 40 andnegative grooves 41 for the waveguides 42 are all formed in a singlemolding process. See FIG. 8A. After the substrate 30 has been molded,the negative grooves 41 are filled with an optically transparentmaterial to form the waveguides 42 (step 74). See FIG. 8B. For example,the negative grooves can be filled using capillary action orover-filling the grooves and then wiping away the excess. In a finalstep 76, the optically transparent material in the grooves is cured,completing the process of making the waveguide substrate 30. Theaforementioned two-step molding process enables the correct amount ofmolding material and optically transparent material to be used in thelocation of the lenses 40 and waveguides 42 respectively. FIGS. 8C and8D show front and top down views of the final structure.

With injection molding embodiment, the substrates 30 are made from anacrylic material having an index of refraction of approximately n=1.5.After the substrates 30 are molded, the negative grooves 41 are filledwith the optically transparent material in one of the manufacturingmethods mentioned herein. The optically transparent material is thencured. Alternatively with compression molding, the substrates 30 aremolded out of a large sheet of substrate material using heat andpressure. When the substrates are pressed, they include the lenses 40and the negative grooves 41 for the waveguides 42. The negative grooves41 are later filled, in the same manner as described above, with anoptically transparent material. In one embodiment, a substrate materialof polycarbonate having an index of refraction of approximately n=1.56is used with compression molding. The optically transparent material, aspreviously noted, has an index of refraction greater than that ofwhatever substrate material is used. It is also preferable, although notabsolutely necessary, that the optically transparent material have theproperties of being optically curable, have a viscosity that can bealtered or controlled if capillary filling of the negative grooves 41 isused, and is inexpensive. In one embodiment, a UV curable material, suchas an optical adhesive urethane from Norland Products, Cranbury, N.J.may be used to fill the negative grooves. Alternatively, an opticalepoxy from a company such as Epoxy Technologies, Billerica, Mass., maybe used. While urethanes and epoxies are mentioned herein, they shouldin no way be construed as limiting the present invention. In variousembodiments, any material having the appropriate index of refraction,clarity, viscosity, surface energy, etc. may be used.

In various embodiments of the invention, the lenses 40 are molded tohave a dimension ranging from 50 to 2000 microns in diameter. Thenegative grooves 41 used to form the waveguides are molded to have adepth 5 to 50 microns deep and 3 to 20 microns wide. The substrate 30can be molded from a variety of materials having an index of refractionranging from 1.0 to 2.0. In one specific embodiment, the negativegrooves are approximately 7.8 microns wide, 20 to 25 microns deep, andhave a slight angle to the walls, ranging from 3 to 5 degrees. Theheight and diameter of the lenses 40 is an arbitrary design choice.Generally speaking, the factors that determine the size of the lenses 40are indexes of refraction of the substrate 30 and the opticallytransparent material, the dimensions of the waveguides 42, and thedesired coupling efficiency of the system. In one specific embodiment,the lenses 40 are 250 microns high and have a diameter ranging from 750microns to 1 millimeter in diameter. It should be noted that all thedimensions provided below are exemplary and in know way should beconstrued as limiting the invention. Lastly, the substrate can be moldedinto any desired shape, including but not limited to, a one dimensionalmember, square, rectangle, circle, oval, etc.

The term molding in this application is intended to be broadlyconstrued. It is intended to cover not only injection and compressionmolding as described above, but also for example embossing and opticalmicro-molding. Embossing is a type of molding where a hot die is forcedonto the molding material. The heat and pressure melts and shapes thesubstrate 30 to assume a desired pattern as defined by the die. Opticalmicro-molding involves the use of light curable materials, such asepoxies and urethanes. Typically the light curable material used for thesubstrate will have a first index of refraction and the backfillmaterial used to fill the negative grooves will have a second index ofrefraction, higher than the first index of refraction. Similarly, theaforementioned embodiments have been described with reference to lenses40. However, any optical element, such as diffraction gratings, filters,bragg gratings, coupling horns as well as lenses can be used. Lastly,the configuration of the substrate 30 is not necessarily limited to the“picture frame” shape illustrated in Figure. The substrate can be moldedto virtually any desired shape, such as but not limited to an elongatedor straight substrate, round, oval, or an L-shaped substrate, etc. TwoL-shaped substrates can be placed together to form the picture framelike structure shown in FIG. 1 for example. The molding of L shapedsubstrates is highly space efficient and would enable the fabrication ofmany substrates in a single molding operation.

The negative grooves can be filled in a number of ways according to thepresent invention. In addition to the filling the grooves and thenwiping away the excess, or using capillary action, other techniques canbe used. For example the substrate 30 be coated with the opticallytransparent material and then etched, leaving the optically transparentmaterial in the grooves. The etching can be performed using ion milling,photo-etch, or a chemical etch. A coating and dipping process may alsobe used. For example, the substrate 30 may be coated with a non-stickingmaterial, such as Teflon, in all areas except the negative grooves. Thecoated substrate is then dipped into a bath of the optically transparentmaterial which sticks in the area of the grooves but does not stickanywhere else.

The present invention provides a number of useful features. Foremost, itis very inexpensive to make. It is also very flexible. The number andlocation of mirrors and waveguides can be readily defined as desired byfabricating molds as needed. The waveguides and the lenses are alsoself-aligning during the molding process. Any problems with opticalalignment are therefore substantially eliminated. Furthermore, thedimension, location, size and optical properties of the lenses 40 andwaveguides 42 can all be easily modified by using a new mold with thedesired features.

Although the foregoing invention has been described in some detail forpurposes of clarity of understanding, it will be apparent that certainchanges and modifications may be practiced within the scope of theappended claims. Therefore, the described embodiments should be taken asillustrative and not restrictive, and the invention should not belimited to the details given herein but should be defined by thefollowing claims and their full scope of equivalents.

1. An apparatus, comprising: a molded substrate body made from a first optically transparent material having: (i) a plurality of integrally molded optical lenses shaped as part of the molded substrate body and made from the first optically transparent material having backside surface and a curved optical face on the side of the lens opposite from the backside surface; and (ii) a plurality of negative grooves molded into the substrate body wherein the grooves terminate at the backside surface of the integrally molded optical lenses and in optical alignment with the plurality of integral lenses, the molded substrate body, the plurality of integral optical lenses, and the plurality of negative grooves form a monolithic waveguide substrate; and a second optically transparent material provided within the plurality of negative waveguide grooves, the optically transparent material forming a plurality of waveguide cores that terminate at the backside surface of the integrally molded optical lenses such that the cores are in contact with and in optical alignment with the plurality of integral optical lenses, each of the plurality of integrally molded optical lenses are molded to taper toward the backside surface of said lens and taper toward an associated one of the plurality of negative grooves so as to contact an associated waveguide core.
 2. The apparatus of claim 1, wherein the plurality of integral optical lenses are three-dimensional lenses.
 3. The apparatus of claim 1, wherein the plurality of integral optical lenses have a dimension ranging from 50 to 2000 microns in diameter.
 4. The apparatus of claim 1, wherein the plurality of waveguide grooves are approximately 5 to 50 microns deep.
 5. The apparatus of claim 1, wherein the plurality of waveguide grooves are approximately 3 to 50 microns wide.
 6. The apparatus of claim 1, wherein the monolithic waveguide substrate and the plurality of integral optical lenses have an index of refraction ranging from n=1.0 to 2.0.
 7. The apparatus of claim 1, wherein the monolithic waveguide substrate and the plurality of integral optical lenses are made from a the first optically transparent material having a first index of refraction and the plurality of grooves are filled with the second optically transparent material having a second index of refraction, wherein the second index of refraction is greater than the first index of refraction.
 8. The apparatus of claim 1, wherein the plurality of optical lenses are configured with optical properties to create a lamina of light when light is provided to inputs of the plurality of waveguides grooves.
 9. The apparatus of claim 1, wherein the plurality of integral optical lenses are configured with optical properties to create a grid of light when light is provided to inputs of the plurality of waveguides grooves.
 10. The apparatus of claim 1, wherein the monolithic waveguide substrate is further configured with a first sub-set of the plurality of waveguide grooves extending in a first direction along a first axis.
 11. The apparatus of claim 10, wherein the monolithic waveguide substrate is further configured with a second sub-set of the plurality of waveguide grooves extending in a second direction along a second axis.
 12. The apparatus of claim 11, wherein the first axis and the second axis are either perpendicular or parallel to each other.
 13. The apparatus of claim 1, wherein the monolithic waveguide substrate is further configured such that the plurality of waveguide grooves extend on a first surface of the monolithic substrate and a second surface of the monolithic substrate, wherein the first surface and the second surface are perpendicular to one another.
 14. The apparatus of claim 1, wherein a first sub-set of the plurality of waveguide grooves are configured to be optically coupled to a light emitter.
 15. The apparatus of claim 1, wherein a first sub-set of the plurality of grooves are configured to be optically coupled to an imaging device.
 16. The apparatus of claim 1, wherein the monolithic waveguide substrate is shaped into one the following shapes: a straight substrate; a square; an L-shaped member, a rectangle, triangle, round, or oval.
 17. The apparatus of claim 1, further comprising: a touch screen device, the monolithic waveguide substrate being configured to create light in the free space adjacent the touch screen device; and an imaging device optically coupled to the light created in the free space adjacent the touch screen device.
 18. The apparatus of claim 17, further comprising a processing device coupled to the imaging device, the processing device configured to determine a data entry to the touch screen by deciphering the coordinates of an interrupt in the light created in the free space adjacent the touch screen device when a data entry is being made to the touch screen device.
 19. The apparatus of claim 1, wherein the monolithic waveguide substrate is formed by one of the following: injection molding; compression molding; embossing; or optical micro-molding.
 20. The apparatus of claim 1, wherein the integral optical lenses comprise the following optical elements: gratings, bragg gratings, coupling horns.
 21. The apparatus of claim 1, wherein the plurality of negative waveguide grooves have angled walls.
 22. The apparatus of claim 1, wherein the angled walls ranges from 3 to 5 degrees.
 23. The apparatus of claim 1, wherein the plurality of negative waveguide grooves are approximately 6 to 8 microns wide and 20 to 25 microns deep.
 24. The apparatus of claim 1, wherein the plurality of integral optical lenses have a height ranging from 40 to 250 microns.
 25. The apparatus of claim 1, wherein the monolithic waveguide substrate is made from a polycarbonate material.
 26. The apparatus of claim 1, wherein the plurality of integral optical lenses have a diameter ranging from 750 microns to 1 millimeter.
 27. The apparatus of claim 1, wherein the first optically transparent material forming the monolithic waveguide substrate is made from a light curable material.
 28. The apparatus of claim 27, wherein the light curable material comprises an epoxy or urethane.
 29. The apparatus of claim 1, wherein the second optically transparent material is a UV curable material.
 30. The apparatus of claim 1, wherein the second optically transparent material consists of an optical adhesive urethane or an optical epoxy.
 31. The apparatus of claim 1, wherein each of the molded optical lenses that form part of the substrate body comprising the first optically transparent material are self-aligned with each associated waveguide core comprising the second optically transparent material.
 32. The apparatus of claim 1, wherein the substrate body has a top planar portion of the surface and wherein the negative grooves are recessed into the substrate body such that the waveguide cores are formed below the top planar portion of the surface and wherein the curved optical faces of the each of the molded optical lenses are oriented so that a portion of the curved optical surface is above said top planar portion and another portion of the curved optical surface is below said top planar portion.
 33. The apparatus of claim 1, wherein each of the molded optical lenses comprise a single lens element.
 34. The apparatus of claim 32, wherein the plurality of integral optical lenses have a height extending above the top planar portion of the surface, said height ranging from 40 to 250 microns. 